One more
This commit is contained in:
Frans Kaashoek
parent
e627608810
commit
26ce97fc76
1 changed files with 0 additions and 123 deletions
123
Notes
123
Notes
|
|
@ -1,123 +0,0 @@
|
|||
bochs 2.2.6:
|
||||
./configure --enable-smp --enable-disasm --enable-debugger --enable-all-optimizations --enable-4meg-pages --enable-global-pages --enable-pae --disable-reset-on-triple-fault
|
||||
bochs CVS after 2.2.6:
|
||||
./configure --enable-smp --enable-disasm --enable-debugger --enable-all-optimizations --enable-4meg-pages --enable-global-pages --enable-pae
|
||||
|
||||
bootmain.c doesn't work right if the ELF sections aren't
|
||||
sector-aligned. so you can't use ld -N. and the sections may also need
|
||||
to be non-zero length, only really matters for tiny "kernels".
|
||||
|
||||
kernel loaded at 1 megabyte. stack same place that bootasm.S left it.
|
||||
|
||||
kinit() should find real mem size
|
||||
and rescue useable memory below 1 meg
|
||||
|
||||
no paging, no use of page table hardware, just segments
|
||||
|
||||
no user area: no magic kernel stack mapping
|
||||
so no copying of kernel stack during fork
|
||||
though there is a kernel stack page for each process
|
||||
|
||||
no kernel malloc(), just kalloc() for user core
|
||||
|
||||
user pointers aren't valid in the kernel
|
||||
|
||||
are interrupts turned on in the kernel? yes.
|
||||
|
||||
pass curproc explicitly, or implicit from cpu #?
|
||||
e.g. argument to newproc()?
|
||||
hmm, you need a global curproc[cpu] for trap() &c
|
||||
|
||||
no stack expansion
|
||||
|
||||
test running out of memory, process slots
|
||||
|
||||
we can't really use a separate stack segment, since stack addresses
|
||||
need to work correctly as ordinary pointers. the same may be true of
|
||||
data vs text. how can we have a gap between data and stack, so that
|
||||
both can grow, without committing 4GB of physical memory? does this
|
||||
mean we need paging?
|
||||
|
||||
perhaps have fixed-size stack, put it in the data segment?
|
||||
|
||||
oops, if kernel stack is in contiguous user phys mem, then moving
|
||||
users' memory (e.g. to expand it) will wreck any pointers into the
|
||||
kernel stack.
|
||||
|
||||
do we need to set fs and gs? so user processes can't abuse them?
|
||||
|
||||
setupsegs() may modify current segment table, is that legal?
|
||||
|
||||
trap() ought to lgdt on return, since currently only done in swtch()
|
||||
|
||||
protect hardware interrupt vectors from user INT instructions?
|
||||
|
||||
test out-of-fd cases for creating pipe.
|
||||
test pipe reader closes then write
|
||||
test two readers, two writers.
|
||||
test children being inherited by grandparent &c
|
||||
|
||||
some sleep()s should be interruptible by kill()
|
||||
|
||||
locks
|
||||
init_lock
|
||||
sequences CPU startup
|
||||
proc_table_lock
|
||||
also protects next_pid
|
||||
per-fd lock *just* protects count read-modify-write
|
||||
also maybe freeness?
|
||||
memory allocator
|
||||
printf
|
||||
|
||||
in general, the table locks protect both free-ness and
|
||||
public variables of table elements
|
||||
in many cases you can use table elements w/o a lock
|
||||
e.g. if you are the process, or you are using an fd
|
||||
|
||||
lock order
|
||||
per-pipe lock
|
||||
proc_table_lock fd_table_lock kalloc_lock
|
||||
console_lock
|
||||
|
||||
do you have to be holding the mutex in order to call wakeup()? yes
|
||||
|
||||
device interrupts don't clear FL_IF
|
||||
so a recursive timer interrupt is possible
|
||||
|
||||
what does inode->busy mean?
|
||||
might be held across disk reads
|
||||
no-one is allowed to do anything to the inode
|
||||
protected by inode_table_lock
|
||||
inode->count counts in-memory pointers to the struct
|
||||
prevents inode[] element from being re-used
|
||||
protected by inode_table_lock
|
||||
|
||||
blocks and inodes have ad-hoc sleep-locks
|
||||
provide a single mechanism?
|
||||
|
||||
kalloc() can return 0; do callers handle this right?
|
||||
|
||||
test: one process unlinks a file while another links to it
|
||||
test: one process opens a file while another deletes it
|
||||
test: deadlock d/.. vs ../d, two processes.
|
||||
test: dup() shared fd->off
|
||||
test: does echo foo > x truncate x?
|
||||
|
||||
sh: ioredirection incorrect now we have pipes
|
||||
sh: chain of pipes won't work, also ugly that parent closes fdarray entries too
|
||||
sh: dynamic memory allocation?
|
||||
sh: should sh support ; () &
|
||||
sh: stop stdin on ctrl-d (for cat > y)
|
||||
|
||||
really should have bdwrite() for file content
|
||||
and make some inode updates async
|
||||
so soft updates make sense
|
||||
|
||||
disk scheduling
|
||||
echo foo > bar should truncate bar
|
||||
so O_CREATE should not truncate
|
||||
but O_TRUNC should
|
||||
|
||||
make it work on a real machine
|
||||
release before acquire at end of sleep?
|
||||
check 2nd disk (i.e. if not in .bochsrc)
|
||||
Loading…
Add table
Reference in a new issue